Apron drive for a tractor scraper

ABSTRACT

A tractor scraper includes a tractor portion and a scraper portion. The scraper portion may include a bowl and an apron disposed adjacent a forward end of the bowl. The tractor scraper may include a first drive configured to raise the apron. The first drive may include an actuator drivingly connected to a pinion. The first drive may also include a rack connected to the apron and the pinion in a manner allowing the actuator to raise the apron by driving the rack with the pinion. The rack may include a plurality of teeth facing rearward.

TECHNICAL FIELD

The present disclosure relates to tractor scrapers and, more particularly, to drives for raising and lowering aprons on tractor scrapers.

BACKGROUND

Tractor scrapers typically include a tractor portion connected to a scraper portion for scraping and transporting material (e.g., soil) from a terrain surface. The scraper portion of a tractor scraper generally includes a bowl with a floor and sides, as well as a blade adjacent a forward end of the floor of the bowl. Such a tractor scraper typically scrapes and gathers material from the terrain surface by driving forward with the blade engaged to the terrain surface and a forward portion of the bowl at least partially open, such that material scraped from the terrain surface by the blade travels across the top of the blade, through the opening in the front of the bowl, onto the floor of the bowl.

To control intake and discharge of material through the front of the bowl, a tractor scraper typically also includes an apron disposed between the sides of the bowl at a forward portion of the bowl, as well as a drive for raising and lowering the apron to open and close the forward portion of the bowl. For example, U.S. Pat. No. 3,016,633 to Le Tourneau (“the '633 patent”) discloses a tractor scraper with such an apron and drive system disposed adjacent a forward end of the bowl. The apron disclosed in the '633 patent has its sides pivotally engaged to the sides of the bowl, and the drive for the apron pivots the apron upward or downward to open or close the front of the bowl.

The drive for the apron in the '633 patent has a rack-and-pinion design. The rack of the system is fixed on the front face of the apron with the teeth of the rack facing forward. The pinion sits in front of the rack with the teeth on the back side of the pinion engaging the forward-facing teeth on the rack. As a motor rotates the pinion, the pinion drives the rack upward or downward, thereby pivoting the rack and the apron upward or downward about the pivot joints connecting the apron to the bowl.

The rack of the apron drive system in the '633 patent is configured in a manner that purportedly helps prevent difficulties associated with soil collecting in the teeth of the rack. The '633 patent discloses making a lower portion of the rack narrower than an upper portion of the rack. The '633 patent indicates that, as the tractor scraper travels forward, soil accumulating in front of the bowl primarily impinges on the lower portion of the rack and not the upper portion of the rack. The '633 patent discloses that the narrow width of the lower portion of the rack reduces the likelihood that the soil impacting the forward-facing teeth on the lower portion of the rack will become lodged in the teeth.

While the '633 patent discloses provisions that purportedly help prevent the soil that impacts the teeth of the rack from becoming lodged in the teeth, certain disadvantages may persist. For example, the placement of the rack on the front of the apron with its teeth facing forward may create a relatively high incidence of soil impacting the teeth of the rack, which may at least partially offset the effect of the narrow width of the lower portion of the rack in the effort to maintain the teeth of the rack clean.

The system and methods of the present disclosure may help address these disadvantages.

SUMMARY

One disclosed embodiment relates to a tractor scraper. The tractor scraper may include a tractor portion and a scraper portion. The scraper portion may include a bowl and an apron disposed adjacent a forward end of the bowl. The tractor scraper may include a first drive configured to raise the apron. The first drive may include an actuator drivingly connected to a pinion. The first drive may also include a rack connected to the apron and the pinion in a manner allowing the actuator to raise the apron by driving the rack with the pinion. The rack may include a plurality of teeth facing rearward.

Another embodiment relates to a method of operating a tractor scraper. The tractor scraper may have a tractor portion and a scraper portion. The scraper portion may include a bowl and an apron disposed adjacent a forward end of the bowl. The method may include raising the apron, which may include supplying power to an actuator to drive a pinion, as well as driving a rack connected to the apron with the pinion, wherein the rack includes a plurality of teeth facing rearward.

A further disclosed embodiment relates to a tractor scraper. The tractor scraper may include a tractor portion and a scraper portion. The scraper portion may include a bowl and an apron disposed adjacent a forward end of the bowl. The apron may have a forward face. The tractor scraper may also include a first drive configured to raise the apron. The first drive may include an actuator drivingly connected to a pinion. The first drive may also include a rack connected to the apron and the pinion in a manner allowing the actuator to raise the apron by driving the rack with the pinion. The rack may be disposed rearward of the forward face of the apron.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of a tractor scraper according to the present disclosure;

FIG. 2 shows a perspective view of a scraper portion of a tractor scraper from one angle;

FIG. 3 shows a perspective view of a forward portion of a scraper portion of a tractor scraper from another angle; and

FIG. 4 is a schematic illustration of one embodiment of a system for powering and controlling an apron drive according to the present disclosure.

DETAILED DESCRIPTION

FIG. 1 shows a tractor scraper 10 according to one embodiment of the present disclosure. Tractor scraper 10 may include a tractor portion 12 and a scraper portion 14. Tractor portion 12 may have a propulsion system for propelling tractor scraper 10. For example, tractor portion 12 may have traction devices 18 (one shown) operably connected to one or more power sources (not shown) for driving propulsion devices 18 to propel tractor portion 12. Traction devices 18 may include any type of components operable to transmit power to a terrain surface 15 underlying tractor scraper 10 to propel it, including, but not limited to, wheels (as shown in FIG. 1) and/or track units. The power sources driving traction devices 18 may include, but are not limited to, one or more engines, transmissions, electric motors, and/or hydraulic motors. Tractor portion 12 may also include an operator's station 20 where an operator may control various aspects of the operation of tractor scraper 10.

Scraper portion 14 may be connected to tractor portion 12 in such a manner that scraper portion 14 moves across terrain surface 15 in concert with tractor portion 12. For example, scraper portion 14 may connect to tractor portion 12 via an articulating hitch 16. Tractor scraper 10 may have various provisions for suspending a rear portion of scraper portion 14 from terrain surface 15. For example, scraper portion 14 may include wheels 32 for supporting a rear portion of scraper portion 14 from terrain surface 15. Alternatively, scraper portion 14 may include one or more track units, skids, or similar components for supporting the rear portion of scraper portion 14 from terrain surface 15.

To suspend the forward portion of scraper portion 14, tractor scraper 10 may include arms 17. A forward end of each arm 17 may connect to hitch 16, and a rearward end of each arm 17 may pivotally connect to scraper portion 14 ahead of wheels 32.

In some embodiments, scraper portion 14 may also include provisions for assisting tractor portion 12 in propelling tractor scraper 10. For example, in some embodiments, scraper portion 14 may include one or more power sources (not shown) driving wheels 32 to assist in propelling tractor scraper 10.

Scraper portion 14 may be configured to gather and haul matter (e.g., soil) from terrain surface 15. Scraper portion 14 may include a bowl 22 for receiving and hauling the gathered matter. FIGS. 2 and 3 illustrate portions of bowl 22 and other components of scraper portion 14 in greater detail. FIG. 2 provides a perspective illustration of scraper portion 14 from the rear and the right side of scraper portion 14, and FIG. 3 provides a closer view of a forward end of scraper portion 14 from the rear and the left side of scraper portion 14. As shown in FIG. 2, bowl 22 of scraper portion 14 may include a right side 24 and a left side 26. As shown in FIG. 3, a spreader member 47 may extend between and connect a front portion of right side 24 and a front portion of left side 26. Bowl 22 may include a floor 28 which may extend between right side 24 and left side 26. At a forward end of floor 28, scraper portion 14 may include a blade 30 for scraping material from terrain surface 15 onto floor 28 of bowl 22 as tractor scraper 10 moves forward. Tractor scraper 10 may have one or more actuators operable under the control of the operator of tractor scraper 10 to raise and lower the front portion of bowl 22 and blade 30 relative to terrain surface 15.

Between the forward ends of right side 24 and left side 26 of bowl 22, scraper portion 14 may include an apron 34. Apron 34 may include a forward face 36 that extends laterally between right side 24 and left side 26 of bowl 22. Forward face 36 of apron 34 may extend rearward as it extends down from its top portion toward blade 30.

Apron 34 may also include a left apron side 38 attached to forward face 36 adjacent left side 26 of bowl 22 and a right apron side 39 attached to forward face 36 adjacent right side 24 of bowl 22. As shown in FIG. 2, left apron side 38 may be pivotally connected to left side 26 of bowl 22 at a pivot joint 40, so that left apron side 38 and forward face 36 may pivot about pivot joint 40. Right apron side 39 may connect to right side 24 of bowl 22 via another pivot joint aligned with pivot joint 40, such that apron 34 may pivot about a lateral axis 41 extending through these pivot joints.

Tractor scraper 10 may include a drive 46 (FIG. 3) and a drive 146 (FIG. 2) for raising and lowering apron 34 to open and close a forward portion of bowl 22 above blade 30. Drive 46 may be a rack-and-pinion type drive having a rack 48, a pinion 50, and an actuator 52 for driving the pinion 50 and rack 48. The components of drive 46 may be mounted to various parts of tractor scraper 10. In some embodiments, rack 48, pinion 50, and actuator 52 may all be fully mounted to scraper portion 14. Actuator 52 and pinion 50 may, for example, mount to an upper portion of left side 26 of bowl 22 (which upper portion of left side 26 is omitted in FIG. 3 to better show left apron side 38). Rack 48 may, for example, mount to apron 34, as discussed in more detail below. Rack 48 may be an elongated member having a plurality of teeth 54 extending along one side thereof. Pinion 50 may be a rotary member having a plurality of teeth engaging teeth 54 of rack 48. Actuator 52 may include any component or components operable to rotate pinion 50 to advance rack 48 in the direction in which teeth 54 extend along rack 48. In some embodiments, actuator 52 may include a rotary motor (such as a hydraulic motor) by itself or in combination with one or more gear-reduction units or other power-transmission components. Exemplary provisions for powering actuator 52 will be discussed in greater detail below in connection with FIG. 4.

As noted above, rack 48 may be mounted to apron 34. As shown in FIG. 3, rack 48 may be mounted rearward of forward face 36 of apron 34. In some embodiments, rack 48 may be mounted to left apron side 38 inward of left side 26 of bowl 22 and rearward of forward face 36 of apron 34. Left apron side 38 may include an indentation 84 away from left side 26 of bowl 22, and rack 48 may be mounted within indentation 84. Rack 48 may be fixedly attached to apron 34, so that apron 34 and rack 48 move as a unit.

Rack 48 may have various shapes and may be oriented in various manners. In some embodiments, rack 48 may have a substantially semicircular shape (e.g., teeth 54 of rack 48 may be disposed in a substantially semicircular arc) and mount to apron 34 in a position substantially concentric to axis 41. Additionally, in some embodiments, indentation 84 may have a substantially semicircular shape that is substantially concentric with axis 41. As also shown in FIG. 3, in some embodiments, teeth 54 of rack 48 may face substantially rearward. Accordingly, to mesh with teeth 54 of rack 48, pinion 50 may be situated directly behind rack 48.

The other drive 146 may have various configurations and may mount to tractor scraper 10 in various manners. For example, drive 146 may be a rack-and-pinion style drive like drive 46. In such embodiments, drive 146 may include an actuator 152, a pinion 150 (shown schematically in FIG. 4), and a rack 148 (shown schematically in FIG. 4) configured and connected to one another and apron 34 in a manner allowing drive 146 to assist drive 46 in raising apron 34 by driving pinion 150 with actuator 152 and driving rack 148 with pinion 150. In some embodiments, drive 146 may be substantially a mirror image of drive 46 but positioned on the right side of scraper portion 14.

FIG. 4 schematically illustrates one embodiment of components that tractor scraper 10 may have for powering and controlling drives 46, 146 to control the position of apron 34. In the example shown in FIG. 4, actuators 52, 152 are reversible, variable-displacement hydraulic motors drivingly connected to pinions 50, 150, and tractor scraper 10 includes a hydraulic system and controls for providing a flow of hydraulic fluid to actuators 52, 152 to drive pinions 50, 150. The components of FIG. 4 for producing a flow of hydraulic fluid for actuators 52, 152 include a reversible, variable-displacement hydraulic pump 74 driven by a power source 76, as well as a hydraulic valve 78 for controlling an amount and a direction of hydraulic fluid flow from the reversible, variable-displacement pump 74 to actuators 52, 152. Power source 76 may be any type of component operable to mechanically drive hydraulic pump 74, including, but not limited to, an internal combustion engine, an electric motor, and a hydraulic motor.

FIG. 4 also schematically illustrates an operator input device 80 and a controller 82 for controlling actuators 52, 152, reversible, variable-displacement hydraulic pump 74, hydraulic valve 78, and power source 76. Operator input device 80 may be any type of component configured for an operator to command up or down movement of apron 34. For example, as shown in FIG. 4, operator input device 80 may be a switch mounted to an operator control handle, which may be located at the operator's station 20 of tractor scraper 10. Operator input device 80 may be operatively connected to controller 82 in such a manner that operator manipulation of operator input device 80 to command up or down movement of apron 34 is communicated to controller 82. Controller 82 may be any type of device operable to receive operator commands to move apron 34 and control one or more other components of tractor scraper 10 to activate actuators 52, 152 to provide the commanded up or down apron movement. In some embodiments, controller 82 may include one or more microprocessors (not shown) and/or one or more memory devices (not shown). Controller 82 may be operatively connected to actuators 52, 152, reversible, variable-displacement hydraulic pump 74, power source 76, and/or hydraulic valve 78. Controller 82 may be configured (e.g., programmed) to control these components to provide operation of actuators 52, 152 consistent with operator commands for up and down movement of apron 34.

A tractor scraper 10 according to the present disclosure is not limited to the exemplary configuration shown in FIGS. 1-4. For instance, rack 48 may have a different configuration and may connect to apron 34 in a different manner and/or position. In some embodiments, rack 48 may connect to apron 34 in a manner allowing relative movement between rack 48 and apron 34. Additionally, actuators 52, 152 may be different kinds of components. For example, in some embodiments, actuators 52, 152 may be fixed-displacement hydraulic motors, rather than variable-displacement hydraulic motors. In some embodiments, actuators 52, 152 may be types of components other than hydraulic motors, such as electric motors. Additionally, tractor scraper 10 may have different components than those shown in FIG. 4 for providing power to actuators 52, 152 and/or controlling actuators 52, 152. For example, pump 74 may be fixed-displacement and non-reversible.

Furthermore, apron 34 may have a different configuration than shown in the figures and/or apron 34 may be connected to tractor scraper 10 in manners other than through pivot joints 40 connecting apron 34 to sides 24, 26 of bowl 22. Similarly, bowl 22 may have a different configuration than shown in the figures. Additionally, tractor scraper 10 may omit one of drives 46, 146 and/or include one or more additional drives for assisting drives 46, 146 in raising and lowering apron 34. Similarly, tractor scraper 10 may have different configurations of components for raising and lowering the front portion of bowl 22, for connecting scraper portion 14 to tractor portion 12, for suspending the rear of scraper portion 14, and/or for propelling tractor scraper 10.

INDUSTRIAL APPLICABILITY

Tractor scraper 10 may have use in any situation where it may prove useful to scrape material from a terrain surface and collect the material in bowl 22. Apron 34 and drives 46, 146 for moving apron 34 may have use in any situation where it may prove helpful to use apron 34 to control intake and discharge of material from the forward end of bowl 22 by closing or opening the forward portion of bowl 22. In many circumstances, an operator of tractor scraper 10 may initially activate drives 46, 146 to raise apron 34 as high as it will go to create an opening in the forward portion of bowl 22 between a lower edge of apron 34 and blade 30 of bowl 22. Subsequently, the operator may lower blade 30 to engage terrain surface 15 and drive tractor scraper 10 forward, so that blade 30 scrapes material from terrain surface 15 and the material scraped from terrain surface 15 accumulates on floor 28 of bowl 22. After at least some material has accumulated in bowl 22, the operator may activate drives 46, 146 to lower apron 34 to reduce or close the opening in the forward portion of bowl 22 to retain the accumulated material in bowl 22 with apron 34. The operator may also raise blade 30 to disengage it from terrain surface 15. Subsequently, the operator may drive tractor scraper 10 to another location and activate drives 46, 146 to raise apron 34 to at least partially open the forward portion of bowl 22. With the apron 34 raised to leave the forward portion of bowl 22 at least partially open, the operator may then discharge material from bowl 22 through the opening at the forward portion of bowl 22.

The operator may command upward or downward movement of apron 34 with operator input device 80. If the operator manipulates operator input device 80 to request upward movement of apron 34, controller 82 may receive this command and adjust the operation of reversible, variable-displacement hydraulic pump 74 and/or hydraulic valve 78 to power actuators 52, 152 to rotate pinions 50, 150 to drive racks 48, 148 upward. For example, actuator 52 may rotate pinion 50 clockwise (from the viewpoint shown in FIG. 3), such that teeth on the front side of pinion 50 push upward on the meshed teeth 54 of rack 48. With racks 48, 148 fixedly attached to apron 34, driving racks 48, 148 upward may also drive apron 34 upward. Specifically, apron 34 and racks 48, 148 may rotate upward around lateral axis 41. With rack 48 having a substantially semicircular shape and being substantially concentric with lateral axis 41, teeth 54 may sequentially pass the same point adjacent pinion 50 as apron 34 rotates upward, keeping rack 54 engaged to pinion 50. If the operator manipulates operator input device 80 to request downward movement of apron 34, controller 82 may adjust the operation of reversible, variable-displacement hydraulic pump 74 and/or hydraulic valve 78 to power actuators 52, 152 to drive racks 48, 148 downward. This may cause racks 48, 148 and apron 34 to rotate downward around pivot axis 34.

The disclosed configuration of tractor scraper 10 and drives 46, 146 may provide a number of advantages. For example, the positioning and orientation of racks 48, 148 may help keep the teeth 54 of racks 48, 148 clean. The material (e.g., soil) that tractor scraper 10 scrapes from terrain surface 15 has the potential to go many places. If the material were to collect in teeth 54 of rack 48, it could interfere with proper meshing of teeth 54 with the teeth of pinion 50. A number of the attributes of the disclosed configuration may tend to prevent this result. Facing teeth 54 rearward may help prevent loose material adjacent the forward end of bowl 22 from collecting in teeth 54 when tractor scraper 10 is travelling forward, as this orientation prevents the teeth 54 from advancing into the material forward of the rack 48. Additionally, nestling rack 48 rearward of forward face 36 of apron 34 between left apron side 38 and left side 26 of bowl 22 within indentation 84 may also help shield rack 48 from loose material in front of, beside, and inside bowl 22. By helping to prevent the material from impacting teeth 54, these features may tend to keep teeth 54 clean.

Additionally, the configuration, positioning, and engagement of racks 48, 148 to pinions 50,150 may help maintain racks 48, 148 properly engaged to pinions 50, 150. Making racks 48, 148 semicircular with their teeth 54 facing rearward and toward the center of curvature may help ensure that tangential forces between teeth 54 of racks 48, 148 and teeth 56 tend to pull racks 48, 148 and pinions 50, 150 toward one another, rather than pushing them apart from one another. This may help maintain pinions 50, 150 properly engaged to racks 48, 148, as well as help reduce overall stress and obviate need for reinforcing components to hold racks 48, 148 and pinions 50, 150 engaged to one another.

The disclosed embodiments also have other advantageous features. For example, mounting actuators 52, 152, pinions 50, 150, and racks 48, 148 all on the scraper portion 14 of tractor scraper 10 may provide certain benefits. In particular, placing these components of drives 46, 146 all on scraper portion 14 may ensure that relative movement between scraper portion 14 and tractor portion 12 does not create unintended movement of apron 34 relative to bowl 22. This may help keep the task of controlling the position of apron 34 simple.

Operation of tractor scraper 10, apron 34, and drives 46, 146 is not limited to the examples discussed above. For instance, racks 48, 148 and apron 34 may move in different manners during upward and downward movement of apron 34. Rather than only pivoting about axis 41, apron 34 and/or racks 48, 148 may translate during upward and downward movement of apron 34. Additionally, in some embodiments, racks 48, 148 may connect to apron 34 in a manner such that relative movement occurs between racks 48, 148 and apron 34 as drives 46, 146 raise and lower apron 34. Furthermore, tractor scraper 10 may provide hydraulic fluid to actuators 52, 152 with different components than those shown in FIG. 4. Alternatively, in embodiments where actuators 52, 152 are not hydraulic motors, tractor scraper 10 may employ means other than hydraulic components to power actuators 52, 152. For example, where actuators 52, 152 are electric motors, tractor scraper 10 may use electrical components to power actuators 52, 152. Furthermore, tractor scraper 10, apron 34, and drives 46, 146 may be controlled other than by a human operator on tractor scraper 10. For example, these systems may be controlled remotely or autonomously.

It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed system and methods without departing from the scope of the disclosure. Other embodiments of the disclosed system and methods will be apparent to those skilled in the art from consideration of the specification and practice of the system and methods disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents. 

1. A tractor scraper, comprising: a tractor portion; a scraper portion disposed rearward of the tractor portion, the scraper portion including a bowl, and an apron disposed adjacent a forward end of the bowl, the apron having a forward face; and a first drive configured to raise the apron, the first drive including an actuator drivingly connected to a pinion, and a rack connected to the apron and operably engaged to the pinion to allow the actuator to raise the apron by driving the rack with the pinion, wherein the rack is disposed rearward of the apron and includes a plurality of teeth facing rearward.
 2. The tractor scraper of claim 1, wherein: the apron includes a side connected to the forward face of the apron and to a side of the bowl; and the rack is attached to the side of the apron.
 3. The tractor scraper of claim 2, wherein: the side of the apron includes an indentation away from the side of the bowl; and the rack is disposed at least partially within the indentation.
 4. The tractor scraper of claim 2, wherein the apron is mounted to the bowl in a manner allowing the apron to pivot about a lateral axis.
 5. The tractor scraper of claim 4, wherein the rack has a substantially semicircular shape.
 6. The tractor scraper of claim 4, wherein the rack has a substantially semicircular shape substantially concentric with the lateral axis.
 7. The tractor scraper of claim 2, wherein the rack is disposed within an indentation of the apron.
 8. The tractor scraper of claim 7, wherein the actuator, the pinion, and the rack are mounted to the scraper portion of the tractor scraper.
 9. The tractor scraper of claim 1, wherein the actuator, the pinion, and the rack are mounted to the scraper portion of the tractor scraper.
 10. The tractor scraper of claim 1, wherein the actuator is a rotary motor.
 11. The tractor scraper of claim 1, further comprising a second drive configured to assist the first drive in raising the apron.
 12. A tractor scraper, comprising: a tractor portion; a scraper portion disposed rearward of the tractor portion, the scraper portion including a bowl, the bowl having a side, and an apron disposed adjacent a forward end of the bowl, the apron having a forward face and a side, the side of the apron being connected to the forward face of the apron and to the side of the bowl in a manner allowing the apron to pivot about a lateral axis, and the side of the apron including an indentation away from the side of the bowl; and a first drive configured to raise the apron, the first drive including an actuator drivingly connected to a pinion, and a substantially semicircular rack disposed substantially concentric to the lateral axis and connected to the side of the apron within the indentation and rearward of the forward face of the apron, the rack being operably engaged to the pinion to allow the actuator to raise the apron by driving the rack with the pinion, wherein the rack includes a plurality of teeth facing rearward.
 13. A tractor scraper, comprising: a tractor portion; a scraper portion disposed rearward of the tractor portion, the scraper portion including a bowl, and an apron disposed adjacent a forward end of the bowl, the apron having a forward face and a side connected to a side of the bowl; and a first drive configured to raise the apron, the first drive including an actuator drivingly connected to a pinion, and a rack connected to the side of the apron and operably engaged to the pinion to allow the actuator to raise the apron by driving the rack with the pinion, wherein the rack is disposed rearward of the forward face of the apron.
 14. The tractor scraper of claim 13, wherein: the side of the apron includes an indentation away from the side of the bowl; and the rack is disposed at least partially within the indentation.
 15. The tractor scraper of claim 13, wherein the apron is mounted to the bowl in a manner allowing the apron to pivot about a lateral axis.
 16. The tractor scraper of claim 15, wherein the rack has a substantially semicircular shape.
 17. The tractor scraper of claim 15, wherein the rack has a substantially semicircular shape substantially concentric with the lateral axis.
 18. The tractor scraper of claim 17, further comprising a second drive configured to assist the first drive in raising the apron.
 19. The tractor scraper of claim 13, further comprising a second drive configured to assist the first drive in raising the apron.
 20. The tractor scraper of claim 13, wherein the actuator, the pinion, and the rack are mounted to the scraper portion of the tractor scraper. 